Digital broadcasting system and method

ABSTRACT

A digital broadcasting system and method, where the digital broadcasting system includes: a transmission stream generator multiplexing a normal stream and a turbo stream to generate a dual transmission stream; a transmitter inserting an supplementary reference signal (SRS) into the dual transmission stream, processing the turbo stream to reconstitute the dual transmission stream, and outputting the reconstituted dual transmission stream; and a receiver receiving the reconstituted dual transmission stream, separately turbo decoding the turbo stream, inserting the turbo decode turbo stream into the dual transmission stream, and decoding the dual transmission stream into which the turbo decoded turbo stream has been inserted, to restore normal stream data and turbo stream data. Thus, reception sensitivity of a digital broadcasting signal can be efficiently improved.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Korean Application No. 2006-68071filed on Jul. 20, 2006, in the Korean Intellectual Property Office, andU.S. Provisional Application Nos. 60/728,777 filed on Oct. 21, 2005;60/734,295 filed on Nov. 8, 2005; 60/738,050 filed on Nov. 21, 2005;60/739,448 filed on Nov. 25, 2005; and 60/788,707 filed on Apr. 4, 2006,the disclosures of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

An aspect of the present invention relates to a digital broadcastingsystem and method using a dual transmission stream including a normalstream and a turbo stream for digital broadcasting, and moreparticularly, to a digital broadcasting system and method for generatingand transmitting a dual transmission stream including a normal streamand a turbo stream to be robustly processed to improve receptionsensitivity of an Advanced Television Systems Committee VestigialSideband (ATSC VSB) way in a United States terrestrial digitaltelevision (DTV) system so as to improve a digital broadcastingperformance.

2. Description of the Related Art

An Advanced Television Systems Committee (ATSC) Vestigial Side Band(VSB) system, that is an American type digital terrestrial broadcastingsystem, is a signal carrier type broadcasting system, and uses a fieldsync signal in the unit of 312 segments. Accordingly, its receptionperformance is not good in an inferior channel, and particularly, in aDoppler fading channel.

FIG. 1 is a block diagram illustrating the construction of atransmitter/receiver of an ATSC DTV standard in a general American typedigital terrestrial broadcasting system. The digital broadcasttransmitter of FIG. 1 is an enhanced VSB (EVSB) system proposed byPhilips, which forms and transmits a dual stream produced by addingrobust data to normal data of the basic ATSC VSB system.

As illustrated in FIG. 1, the digital broadcast transmitter includes arandomizer 11 randomizing a dual stream, a Reed-Solomon (RS) encoder 12in the form of a concatenated coder that adds parity bytes to thetransport stream in order to correct errors that occur, due to thechannel characteristic, in a transport process, an interleaver 13interleaving the RS-encoded data according to a specified pattern, and a⅔-rate trellis encoder 14 mapping the interleaved data onto 8-levelsymbols by performing a ⅔-rate trellis encoding of the interleaved data.The digital broadcast transmitter performs an error correction coding ofthe dual stream.

The digital broadcast transmitter further includes a multiplexer 15inserting a field sync signal and a segment sync signal into theerror-correction-coded data as illustrated in FIG. 2, and a modulator 16inserting a pilot tone into the data symbols, into which the segmentsync signal and the field sync signal have been inserted by adding aspecified DC value to the data symbols, performing a VSB modulation ofthe data symbols by pulse-shaping the data symbols, and up-convertingthe modulated data symbols into an RF channel band signal to transmitthe RF channel band signal.

In the digital broadcast transmitter, the normal data and the robustdata are multiplexed (not illustrated) according to a dual stream systemand the normal data and the robust data are transmitted through onechannel, and the multiplexed data is inputted to the randomizer 11. Theinput data is randomized through the randomizer 11, outer-encodedthrough the RS encoder 12 that is an outer encoder, and then distributedthrough the interleaver 13.

Also, the interleaved data is inner-encoded in the unit of 12 symbolsthrough the trellis encoder 14, and then mapped onto the 8 levelsymbols. After the field sync signal and the segment sync signal areinserted into the coded data, the data is VSB-modulated by inserting apilot tone into the data, and converted into an RF signal.

On the other hand, the digital broadcast receiver of FIG. 1 includes atuner (not illustrated) converting an RF signal received through achannel into a baseband signal, a demodulator 21 performing a syncdetection and demodulation of the converted baseband signal, anequalizer 22 compensating for a channel distortion of the demodulatedsignal occurring due to a multi-path, a Viterbi decoder 23 correctingerrors of the equalized signal and decoding the error-corrected signalto symbol data, a deinterleaver 24 rearranging the data distributed bythe interleaver 13 of the digital broadcast transmitter, an RS decoder25 correcting errors, and a derandomizer 26 derandomizing the datacorrected through the RS decoder 25 and outputting an MPEG-2 transportstream.

Accordingly, the digital broadcast receiver of FIG. 1 down-converts theRF signal into the baseband signal, demodulates and equalizes theconverted signal, and then channel-decodes the demodulated signal torestore the original signal.

FIG. 2 illustrates a VSB data frame for use in the American type digitalbroadcasting (8-VSB) system, into which a segment sync signal and afield sync signal are inserted. As shown in FIG. 2, one frame iscomposed of two fields, and each field is composed of one field syncsegment, that is the first segment, and 312 data segments. Also, onesegment in the VSB data frame corresponds to one MPEG-2 packet, and iscomposed of a segment sync signal of four symbols and 828 data symbols.

In FIG. 2, the segment sync signal and the field sync signal are usedfor the synchronization and equalization in the digital broadcastreceiver. That is, the field sync signal and the segment sync signalrefer to known data between the digital broadcast transmitter andreceiver, which is used as a reference signal when the equalization isperformed in the receiver side.

The American type digital terrestrial broadcasting system as illustratedin FIG. 1 is a system that can form and transmit a dual stream producedby adding the robust data to the normal data of the existing ATSC VSBsystem. This system transmits the robust data together with the existingnormal data.

However, the American type digital terrestrial broadcasting system ofFIG. 1 has almost no effect in improving the inferior receptionperformance in a multipath channel due to the transmission of theexisting normal data, although the American type digital terrestrialbroadcasting system transmits the dual stream produced by adding therobust data to the normal data.

That is, the American type digital terrestrial broadcasting system hasalmost no effect in improving the reception performance according to theimprovement of the normal stream. Also, even with respect to a turbostream, it does not have a great effect in improving the receptionperformance in a multipath environment.

In addition, according to the conventional digital broadcasting system,it is impossible to confirm the channel state between a transmitter sideand a receiver side.

SUMMARY OF THE INVENTION

Accordingly, the present general inventive concept has been made tosolve the above-mentioned and/or other problems, and an aspect of thepresent general inventive concept is to provide a digital broadcastingsystem and method capable of improving reception sensitivity of anAdvanced Television Systems Committee Vestigial Sideband (ATSC VSB) wayin a United States terrestrial digital television (DTV) system.

According to an aspect of the present invention, there is provided adigital broadcasting system including: a transmission stream generatormultiplexing a normal stream and a turbo stream to generate a dualtransmission stream; a transmitter inserting a supplementary referencesignal (SRS) into the dual transmission stream, processing the turbostream to reconstitute the dual transmission stream, and outputting thereconstituted dual transmission stream; and a receiver receiving thereconstituted dual transmission stream, separately turbo decoding theturbo stream, inserting the turbo decode turbo stream into the dualtransmission stream, and decoding the dual transmission stream intowhich the turbo decoded turbo stream has been inserted, to restorenormal stream data and turbo stream data.

The transmission stream generator may include: an Reed-Solomon (RS)encoder receiving the turbo stream from an external source and RSencoding the turbo stream; a duplicator forming a parity insertion areain the RS encoded turbo stream; and a multiplexer receiving the normalstream from an external source and multiplexing the turbo streamprocessed by the duplicator and the normal stream to generate the dualtransmission stream.

The duplicator may convert each byte of the turbo stream using a ½ rateconversion method or a ¼ rate conversion method to form the parityinsertion area between data bits of the turbo stream.

The transmitter may include: a randomizer receiving the dualtransmission stream from the transmission stream generator andrandomizing the dual transmission stream; an SRS inserter inserting anSRS into a stuffing area formed in the randomized dual transmissionstream; an RS encoder encoding the dual transmission stream into whichthe SRS has been inserted; an interleaver interleaving the encoded dualtransmission stream; a turbo processor detecting the turbo stream fromthe interleaved dual transmission stream, encoding the detected turbostream, stuffing the encoded turbo stream into the dual transmissionstream, and compensating for parity corresponding to the encoded turbostream; and a trellis and/or parity corrector trellis encoding the dualtransmission stream processed by the turbo processor.

The turbo processor may include: a turbo stream detector detecting theturbo stream from the interleaved dual transmission stream; an outerencoder inserting parity corresponding to the detected turbo stream intothe parity insertion area of the turbo stream; an outer interleaverinterleaving the turbo stream into which the parity has been inserted; aturbo stream stuffer inserting the interleaved turbo stream into thedual transmission stream to reconstitute the dual transmission stream;and a parity compensator regenerating parity of the reconstituted dualtransmission stream and adding the parity to the dual transmissionstream.

The turbo processor further includes: a byte-symbol converter convertingthe interleaved dual transmission stream from a byte unit into a symbolunit; and a symbol-byte converter converting the dual transmissionstream including the parity regenerated by the parity compensator from asymbol unit into a byte unit.

The transmitter may further include: a multiplexer adding a sync signalto the trellis encoded dual transmission stream; a pilot inserterinserting a pilot into the dual transmission stream to which the syncsignal has been added; a pre-equalizer equalizing the dual transmissionstream into which the pilot has been inserted; a Vestigial Sideband(VSB) modulator VSB modulating the equalized dual transmission stream;and a radio frequency (RF) modulator modulating the VSB modulated dualtransmission stream into a signal in an RF channel band and transmittingthe signal.

The trellis and/or parity corrector may perform an initialization beforeencoding the SRS and compensates for the parity according to a valuechanged by the initialization.

The trellis and/or parity corrector may include: a trellis encoder blockperforming the initialization and outputting a pre-stored value as aninitial value if an external control signal corresponding to aninitialization section is received; an RS re-encoder generating paritycorresponding to the initial value; an adder adding the parity generatedby the RS re-encoder to the dual transmission stream to correct parityof the dual transmission stream; a multiplexer providing the dualtransmission stream including the parity corrected by the adder to thetrellis encoder block; and a mapper symbol mapping and outputting thedual transmission stream trellis encoded by the trellis encoder block.

The trellis encoder block may include: a plurality of trellis encoders;a splitter sequentially inputting the dual transmission stream into theplurality of trellis encoders; and an encoding output unit sequentiallydetecting values encoded by the plurality of trellis encoders.

Each of the plurality of trellis encoders may include: a first memoryinitialized and outputting a pre-stored value as a first initial valueif the external control signal is input; a second memory; and a thirdmemory initialized to shift a pre-stored value to the second memory soas to output a value pre-stored in the second memory as a second initialvalue if the external control signal is input, wherein the RS re-encodergenerates parity corresponding to an initial value including acombination of the first and second initial values.

The receiver may include: a demodulator receiving and demodulating thedual transmission stream including the turbo stream and the normalstream; an equalizer equalizing the demodulated dual transmissionstream; a Viterbi decoder decoding the normal stream of the equalizeddual transmission stream; a turbo decoder decoding the turbo stream ofthe equalized dual transmission stream; a turbo inserter inserting theturbo stream decoded by the turbo decoder into the dual transmissionstream output from the Viterbi decoder; a deinterleaver deinterleavingthe dual transmission stream processed by the turbo inserter; an RSdecoder RS decoding the deinterleaved dual transmission stream; aderandomizer derandomizing the RS decoded dual transmission stream; anda turbo demultiplexer demultiplexing the derandomized dual transmissionstream to restore a normal stream packet and a turbo stream packet.

The turbo decoder may include: a trellis decoder trellis decoding theturbo stream of the equalized dual transmission stream; an outerdeinterleaver deinterleaving the trellis decoded turbo stream; an outermap decoder decoding the deinterleaved turbo stream; an outerinterleaver interleaving the turbo stream decoded by the outer mapdecoder and providing the interleaved turbo stream to the trellisdecoder if the outer map decoder outputs a soft decision output value;and a frame formatter frame formatting a hard decision output valueoutput from the outer map decoder.

The turbo decoder may further include a symbol deinterleaver convertingthe frame formatted turbo stream from a symbol unit into a byte unit andproviding the turbo stream to the turbo inserter.

The turbo demultiplexer may include: a transmission stream (TS)demultiplexer demultiplexing the dual transmission stream to output thenormal stream and the turbo stream; a first sync signal inserterinserting a sync signal into the normal stream output from the TSdemultiplexer and outputting the normal stream including the syncsignal; a condenser removing a placeholder from the turbo stream outputfrom the TS demultiplexer; an RS decoder RS decoding the turbo streamfrom which the placeholder has been removed; and a second sync signalinserter inserting a sync signal into the RS decoded turbo stream andoutputting the turbo stream including the sync signal.

The turbo demultiplexer may include: a TS demultiplexer demultiplexingthe dual transmission stream to output the normal stream and the turbostream; a sync signal inserter inserting a sync signal into the normalstream output from the TS demultiplexer and outputting the normal streamincluding the sync signal; a condenser removing a placeholder from theturbo stream output from the TS demultiplexer; a sync signal detectordetecting a sync signal from the turbo stream from which the placeholderhas been removed; and an RS decoder RS decoding the turbo stream fromthe detected sync signal up to a predetermined length and outputting thedecoded turbo stream.

According to another aspect of the present invention, there is provideda digital broadcasting method including: multiplexing a normal streamand a turbo stream to generate a dual transmission stream; inserting anSRS into the dual transmission stream, processing the turbo stream toreconstitute the dual transmission stream, and outputting thereconstituted dual transmission stream; and receiving the reconstituteddual transmission stream, separately turbo decoding the turbo stream,inserting the turbo decoded turbo stream into the dual transmissionstream, and decoding the dual transmission stream into which the turbodecoded turbo stream has been inserted, to restore normal stream dataand turbo stream data.

The multiplexing of the normal stream and the turbo stream to generatethe dual transmission stream may include: receiving the turbo streamfrom an external source and RS encoding the turbo stream; forming aparity insertion area in the RS encoded turbo stream; and receiving thenormal stream from an external source and multiplexing the turbo streamincluding the parity insertion area and the normal stream to generatethe dual transmission stream.

Each byte of the turbo stream may be converted using a ½ rate conversionmethod or a ¼ rate conversion method to form the parity insertion areabetween data bits of the turbo stream.

The inserting of the SRS into the dual transmission stream, processingthe turbo stream to reconstitute the dual transmission stream, and theoutputting of the reconstituted dual transmission stream may include:randomizing the generated dual transmission stream; inserting the SRSinto a stuffing area formed in the randomized dual transmission stream;encoding the dual transmission stream into which the SRS has beeninserted; interleaving the encoded dual transmission stream; detectingthe turbo stream from the interleaved dual transmission stream, encodingthe turbo stream, stuffing the encoded turbo stream into the dualtransmission stream, and compensating for parity corresponding to theencoded turbo stream; and trellis encoding the turbo processed dualtransmission stream.

The detecting of the turbo stream from the interleaved dual transmissionstream, the encoding of the turbo stream, the stuffing of the encodedturbo stream into the dual transmission stream, and the compensating forthe parity corresponding to the encoded turbo stream may include:detecting the turbo stream from the interleaved dual transmissionstream; inserting parity corresponding to the detected turbo stream intothe parity insertion area of the turbo stream; interleaving the turbostream into which the parity has been inserted; inserting theinterleaved turbo stream into the dual transmission stream toreconstitute the dual transmission stream; and regenerating parity ofthe reconstituted dual transmission stream and adding the parity to thedual transmission stream to compensate for the parity.

The detecting of the turbo stream from the interleaved dual transmissionstream, the encoding of the turbo stream, the stuffing of the encodedturbo stream into the dual transmission stream, and the compensating forthe parity corresponding to the encoded turbo stream may furtherinclude: converting the interleaved dual transmission stream from a byteunit into a symbol unit; and converting the dual transmission streamincluding the regenerated parity from a symbol unit into a byte unit.

The inserting of the SRS into the dual transmission stream, processingthe turbo stream to reconstitute the dual transmission stream, and theoutputting of the reconstituted dual transmission stream may furtherinclude: adding a sync signal to the trellis encoded dual transmissionstream; inserting a pilot into the dual transmission stream to which thesync signal has been added; equalizing the dual transmission stream intowhich the pilot has been inserted; VSB modulating the equalized dualtransmission stream; and modulating the VSB modulated dual transmissionstream into a signal in an RF channel band and transmitting the signal.

In the trellis encoding, an initialization may be performed before theSRS is encoded and the parity may be compensated for according to avalue changed by the initialization.

The receiving of the reconstituted dual transmission stream, theseparately turbo decoding of the turbo stream, the inserting of theturbo decode turbo stream into the dual transmission stream, and thedecoding of the dual transmission stream into which the turbo decodedturbo stream has been inserted, to restore normal stream data and turbostream data may include: receiving and demodulating the dualtransmission stream including the turbo stream and the normal stream;equalizing the demodulated dual transmission stream; Viterbi decodingthe normal stream of the equalized dual transmission stream; turbodecoding the turbo stream of the equalized dual transmission stream;inserting the turbo decoded turbo stream into the Viterbi decoded dualtransmission stream; deinterleaving the dual transmission stream intowhich the turbo decoded turbo stream has been inserted; RS decoding thedeinterleaved dual transmission stream; derandomizing the RS decodeddual transmission stream; and demultiplexing the derandomized dualtransmission stream to restore a normal stream packet and a turbo streampacket.

The turbo decoding of the turbo stream of the equalized dualtransmission stream may include: trellis decoding the turbo stream ofthe equalized dual transmission stream; deinterleaving the trellisdecoded turbo stream; decoding the deinterleaved turbo stream; and if ahard decision output value is output during the decoding of thedeinterleaved turbo stream, frame formatting the hard decision outputvalue, wherein the trellis decoding of the turbo stream of the equalizeddual transmission stream, the deinterleaving of the trellis decodedturbo stream, and the decoding of the deinterleaved turbo stream arerepeated until the hard decision output value is output during thedecoding of the deinterleaved turbo stream.

The turbo decoding of the turbo stream of the equalized dualtransmission stream may further include converting the frame formattedturbo stream from a symbol unit into a byte unit.

The demultiplexing of the derandomized dual transmission stream torestore the normal stream packet and the turbo stream packet mayinclude: demultiplexing the dual transmission stream to split the normalstream and the turbo stream from the dual transmission stream; insertinga sync signal into the split normal stream and outputting the normalstream including the sync signal; removing a placeholder from the splitturbo stream and RS decoding the turbo stream; and inserting a syncsignal into the RS decoded turbo stream and outputting the inserted syncsignal.

The demultiplexing of the derandomized dual transmission stream torestore the normal stream packet and the turbo stream packet mayinclude: demultiplexing the dual transmission stream to split the normalstream and the turbo stream from the dual transmission stream; insertinga sync signal into the split normal stream and outputting the normalstream including the sync signal; removing a placeholder from the splitturbo stream and RS decoding the turbo stream; and detecting a syncsignal from the turbo stream from which the placeholder has beenremoved, RS decoding the turbo stream from the detected sync signal upto a predetermined length, and outputting the RS decoded turbo stream.

Additional aspects and/or advantages of the invention will be set forthin part in the description which follows and, in part, will be obviousfrom the description, or may be learned by practice of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects and advantages of the invention will becomeapparent and more readily appreciated from the following description ofthe embodiments, taken in conjunction with the accompanying drawings ofwhich:

FIG. 1 is a block diagram illustrating a configuration of a conventionaldigital broadcasting (ATSC VSB) transmitting and receiving system;

FIG. 2 is a view illustrating a frame structure of conventional AdvancedTelevision Systems Committee Vestigial Sideband (ATSC VSB) data;

FIG. 3 is a block diagram illustrating a configuration of a digitalbroadcasting system according to an embodiment of the present invention;

FIG. 4 is a block diagram illustrating a configuration of a transmissionstream generator of the digital broadcasting system shown in FIG. 3,according to an embodiment of the present invention;

FIG. 5 is a view illustrating a structure of a stream output from an RSencoder of the transmission stream generator shown in FIG. 3, accordingto an embodiment of the present invention;

FIGS. 6 and 7 are views illustrating a process of generating parityinsertion areas using the transmission stream generator shown in FIG. 4,according to embodiments of the present invention;

FIG. 8 is a block diagram illustrating a configuration of a transmitterof the digital broadcasting system shown in FIG. 3, according to anembodiment of the present invention;

FIGS. 9 and 10 are block diagrams illustrating a configuration of aturbo processor used in the transmitter shown in FIG. 8, according toembodiments of the present invention;

FIG. 11 is a view illustrating an operation of an outer interleaver usedin a turbo processor according to an embodiment of the presentinvention;

FIG. 12 is a block diagram illustrating a configuration of a trellisand/or parity corrector used in the transmitter shown in FIG. 8,according to an embodiment of the present invention;

FIG. 13 is a block diagram illustrating a configuration of a trellisencoder block used in the trellis and/or parity corrector shown in FIG.12, according to an embodiment of the present invention;

FIG. 14 is a block diagram illustrating a configuration of a receiver ofthe digital broadcasting system shown in FIG. 3, according to anembodiment of the present invention;

FIG. 15 is a block diagram illustrating a configuration of a turbodecoder shown in FIG. 14, according to an embodiment of the presentinvention;

FIGS. 16 and 17 are block diagrams illustrating a configuration of aturbo demultiplexer shown in FIG. 14, according to embodiments of thepresent invention;

FIG. 18 is a flowchart illustrating a process of transmitting a dualtransmission stream according to an embodiment of the present invention;

FIG. 19 is a flowchart illustrating a process of receiving a dualtransmission stream according to an embodiment of the present invention;

FIG. 20 is a flowchart illustrating a turbo decoding process accordingto an embodiment of the present invention; and

FIG. 21 is a view illustrating a structure of a dual transmission streamprocessed by a digital broadcasting system according to an embodiment ofthe present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Reference will now be made in detail to the present embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings, wherein like reference numerals refer to the like elementsthroughout. The embodiments are described below in order to explain thepresent invention by referring to the figures.

FIG. 3 is a block diagram illustrating a configuration of a digitalbroadcasting system according to an embodiment of the present invention.Referring to FIG. 3, the digital broadcasting system includes atransmission stream generator 100, a transmitter 200, and a receiver300.

The transmission stream generator 100 receives and multiplexes a normalstream and a turbo stream to generate a dual transmission stream.

FIG. 4 is a block diagram illustrating a configuration of thetransmission stream generator 100 shown in FIG. 4, according to anembodiment of the present invention. Referring to FIG. 4, thetransmission stream generator 100 includes an RS encoder 110, aduplicator 120, and a multiplexer 130.

The RS encoder 110 receives the turbo stream, adds parity to the turbostream, encodes the turbo stream, and transmits the encoded turbo streamto the duplicator 120.

FIG. 5 is a view illustrating a structure of a packet encoded by the RSencoder 110 shown in FIG. 4. The RS encoder 110 shown in FIG. 4 receivesthe turbo stream including a sync signal area, a packet identity (PID)area, and a turbo data area. The whole turbo stream packet may include188 bytes. Here, a sync signal may be 1 byte, PID may be 3 bytes, andturbo data may be 184 bytes. The RS encoder 110 removes the sync signalfrom the turbo stream, computes parity of the turbo data area, and addsparity of 20 bytes to the turbo stream. As a result, a packet of thefinally encoded turbo stream includes 207 bytes. Here, 3 bytes of 207bytes are allocated to the PID, 184 bytes are allocated to turbo data,and 20 bytes are allocated to parity.

The duplicator 120 forms parity insertion areas in the encoded turbostream. A method of forming the parity insertion area will now bedescribed in detail. Bytes of the turbo stream are divided into groupseach having 2 bytes or 4 bytes. A portion of bit values of one byte andnull data (e.g., “0”) are put into each of the groups. Areas into whichnull data is input are the parity insertion areas.

The operation of the duplicator 120 will now be described in moredetail. In other words, if an input is increased to two times and “a, b,c, d, e, f, g, h” are inserted into one byte in order from mostsignificant bits (MSB), an output of the duplicator 120 may be expressedas “a, a, b, b, c, c, d, d, e, e, f, f, g, g, h, h.” In this case, onebyte including MSBs “a, a, b, b, c, c, d, d” and one byte including bits“e, e, f, f, g, g, h, h” are sequentially output.

If an input is increased to four times, an output of the duplicator 120may be expressed as “a, a, a, a, b, b, b, b, c, c, c, c, d, d, d, d, e,e, e, e, f, f, f, f, g, g, g, g, h, h, h, h.” In other words, 4 bytesare output. The duplicator 120 does not need to necessarily duplicateinput bits but may insert a different arbitrary value, i.e., null data,into other positions except designated positions. For example, if theduplicator 120 increases an input to two times, the duplicator 120 mayoutput “a, x, b, x, c, x . . . ” instead of “a, a, b, b, c, c, . . . .”In other words, the duplicator 120 may maintain an original input valueonly in a fore part of each of two consecutive bits but may put anarbitrary value into a back part of each of the two consecutive bits.

In an opposite case, the duplicator 120 may maintain an original valueonly in the back part. If the duplicator 120 increases an output to fourtimes, an original input may be put only into one of first throughfourth positions, and an arbitrary value may be put into the otherpositions.

FIGS. 6 and 7 are views illustrating a method of forming parityinsertion areas using the duplicator 120, according to an embodiment ofthe present invention. FIG. 6 illustrates a ½ rate conversion method.The duplicator 120 adopts a ½ rate conversion method to each byte of aturbo stream to generate two bytes. As shown in FIG. 6, one byteincluding bits D₀ through D₇ is divided into two bit groups. One of thetwo bit groups includes 4 bits D₀ through D₃, and the other one includes4 bits D₄ through D₇. In this state, one null bit is arranged with eachbit of each of the two bit groups to expand each of the two bit groupsto a byte. As a result, a first byte “D7 0 D6 0 D5 0 D4 0” includingbits D₄ through D₇ and a second byte “D3 0 D2 0 D1 0 0” including D₀through D₃ are generated. A bit between two bits of each of the firstand second bytes is used as a parity insertion area. In other words,second, fourth, sixth, and eighth bits of each of the first and secondbytes are used as parity insertion areas. Positions of such parityinsertion areas may vary. In other words, second, third, sixth, andseventh bits or third, fourth, fifth, and sixth bits may be used asparity insertion areas.

FIG. 7 illustrates a ¼ rate conversion method. The duplicator 120 adoptsa ¼ rate conversion method to each byte of the turbo stream to generatefour bytes. Referring to FIG. 7, one byte including bits D₀ through D₇is divided into four bit groups each having two bits D₀ and D₁, D₂ andD₃, D₄ and D₅, or D₆ and D₇. In this state, three null bits are arrangedin a line next to each bit of each of the four bit groups to expand eachof the four bit groups to a byte. In detail, one byte is expanded to afirst byte “D7 0 0 0 D6 0 0 0” including D₆ and D₇, a second byte “D5 00 0 D4 0 0 0” including D₄ and D₅, a third byte “D3 0 0 0 D2 0 0 0”including D₂ and D₃, and fourth byte “D1 0 0 0 D0 0 0 0” including D₀and D₁. Referring to FIG. 7, second, third, fourth, sixth, seventh, andeighth bits of each of the four bit groups are used as parity insertionareas, but parity insertion areas are limited to this case.

Referring to FIG. 4, the multiplexer 130 multiplexes the normal streamadditionally received and the turbo stream processed by the duplicator120. Thus, a dual transmission stream including the normal stream andthe turbo stream may be generated. The normal stream and the turbostream may be received from an external module such as a broadcastshooting apparatus or the like or an internal module such as acompression processing module, e.g., a Moving Picture Experts Group-2(MPEG-2) module, a video encoder, an audio encoder, or the like.

The multiplexer 130 forms an adaptation field in each packet of the dualtransmission stream. The adaptation field refers to an area in which aturbo stream or other data is to be inserted. In detail, besides a turbostream, reset data for initialization, a supplementary reference signal(SRS), or the like may be inserted into the adaptation field. Theadaptation field may be used as an option field in which various typesof packet information are recorded. Packet information may be a programclock reference (PCR), an original program clock reference (OPCR), fourcircuit blocks, a splice countdown, a transport private data length, oran adaptation field extension length. The PCR is used for asynchronization of a demodulator of a receiver. The OPCR is used torecord, reserve, and play a program in a receiver. The splice countdownis a number of consecutive macro-blocks each including Cr (redchrominance) and Cb (blue chrominance) blocks. The transport privatedata length is a length of letter data of letter broadcasting. In thiscase, an area in which a turbo stream is to be recorded may not overlapwith the option field.

The transmission stream generator 100 shown in FIG. 4 may furtherinclude an interleaver (not shown). In this case, the interleaver may bedisposed before or after the duplicator 120. Thus, the RS encoded turbostream may be interleaved, and then the parity insertion areas may begenerated. Alternatively, the turbo stream in which the parity insertionareas have been generated may be interleaved and then provided to themultiplexer 130.

The transmitter 200 shown in FIG. 3 may be realized as shown in FIG. 8.

Referring to FIG. 8, the transmitter 200 includes a randomizer 210, anSRS inserter 220, an RS encoder 230, an interleaver 240, a turboprocessor 250, a trellis and/or parity corrector 260, a sync signalmultiplexer 270, a pilot inserter 280, a pre-equalizer 285, a vestigialsideband (VSB) modulator 290, and an RF modulator 295.

The randomizer 210 randomizes the dual transmission stream received fromthe transmission stream generator 100.

The SRS inserter 220 receives the dual transmission stream and insertsan SRS into an adaptation field of each packet of the dual transmissionstream. The SRS refers to a signal pattern commonly known to atransmitter and a receiver. A broadcasting receiver compares an SRS of areceived stream with an existing SRS to easily check a state of achannel. Thus, a degree of a compensation for parity may be determined.

The RS encoder 230 encodes the dual transmission stream into which theSRS has been inserted.

The interleaver 240 interleaves the encoded dual transmission stream.

The turbo processor 250 detects only the turbo stream from theinterleaved dual transmission stream, encodes and interleaves thedetected turbo stream, and robustly processes the encoded andinterleaved turbo stream. Next, the robustly processed turbo stream isstuffed into the dual transmission stream to reconstitute the dualtransmission stream. Thereafter, a compensation operation is performedon parity changed by the encoding of the turbo stream. Examples of theconfiguration of the turbo processor 250 are shown in FIGS. 9 and 10.

Referring to FIG. 9, the turbo processor 250 includes a turbo streamdetector 251, an outer encoder 252, an outer interleaver 253, a turbostream stuffer 254, and a parity compensator 255.

The turbo stream detector 251 detects the turbo stream from the dualtransmission stream.

The outer encoder 252 adds parity into the parity insertion areas of thedetected turbo stream to encode the turbo stream.

The outer interleaver 253 interleaves the encoded turbo stream.

The turbo stream stuffer 254 multiplexes the interleaved turbo streamand the normal stream to reconstitute the dual transmission stream. Theturbo stream stuffer 254 may be realized as a multiplexer.

The parity compensator 255 regenerates parity of the reconstituted dualtransmission stream and adds the parity to the dual transmission streamso as to compensate for a parity error caused by the encoding of theturbo stream.

FIG. 10 is a block diagram illustrating a configuration of the turboprocessor 250 according to another embodiment of the present invention.Referring to FIG. 10, the turbo processor 250 may further include abyte-symbol converter 256 and a symbol-byte converter 257 besides aturbo stream detector 251, an outer encoder 252, an outer interleaver253, a turbo stream stuffer 254, and a parity compensator 255.

The byte-symbol converter 256 converts the dual transmission streaminterleaved by the interleaver 240 from a byte unit into a symbol unit.The conversion from the byte unit into the symbol unit may be easilyunderstood with reference to Table D5.2 of “US ATSC DTV Standards(A/53).” The turbo stream detector 251 detects the turbo stream from thedual transmission stream which has been converted into the symbol unit.The outer encoder 252 computes parity of the detected turbo stream andinserts the parity into a parity insertion area to encode the turbostream. In this case, the outer encoder 252 encodes the turbo stream inthe unit of byte.

The outer interleaver 253 interleaves the encoded turbo stream. In thiscase, the outer interleaver 253 interleaves the encoded turbo stream inthe unit of bit.

The turbo stream stuffer 254 multiplexes the interleaved turbo streamand the normal stream to constitute the dual transmission stream. Indetail, the turbo stream stuffer 254 stuffs the turbo stream into aposition of the turbo stream which is not detected by the turbo streamdetector 251 to constitute the dual transmission stream.

The symbol-byte converter 257 converts the dual transmission stream froma symbol unit into a byte unit. The conversion from the symbol unit intothe byte unit may be easily understood with reference to Table D5.2 of“US ATSC DTV Standards (A/53).”

FIG. 11 is a view illustrating an interleaving process performed by theouter interleaver 253. Referring to FIG. 11, the outer interleaver 253performs interleaving according to a predetermined interleaving rule.For example, the predetermined interleaving rule is {0, 1, 2, 3}=>{2, 1,3, 0} and “A, B, C, and D” are sequentially input, “A, B, C, and D” areinterleaved and output in the format of “DBAC.”

Referring to FIG. 8, the turbo processed dual transmission stream istrellis encoded by the trellis and/or parity corrector 260. The trellisand/or parity corrector 260 also corrects parity changed by the trellisencoding.

FIG. 12 is a block diagram illustrating a configuration of the trellisand/or parity corrector 260 according to an embodiment of the presentinvention. Referring to FIG. 12, the trellis and/or parity corrector 260includes a trellis encoder block 410, an RS re-encoder 420, an adder430, a multiplexer 440 and a mapper 450.

The multiplexer 440 may have an operation mode (referred to as a commonmode) in which trellis encoding is performed and an operation mode(referred to as a parity correction mode) in which a packet added by theadder 430 is trellis encoded. The operation modes of the multiplexer 440depend on a control signal received from the RS re-encoder 420.

The trellis encoder block 410 trellis encodes a packet received from themultiplexer 440. The trellis encoder block 410 may trellis encode thepacket according to an external control signal and may be initializedimmediately before SRS data of the packet is trellis encoded.

The RS re-encoder 420 regenerates parity corresponding to the changedpacket when the trellis encoder block 410 is initialized.

The adder 430 adds the re-encoded parity to the packet received from theturbo processor 250 and provides the addition result to the multiplexer440. The addition method will now be described.

-   A) The fore is omitted . . . 101001010111001010101011AAAAA . . . .    The rest is omitted.-   B) The fore is omitted . . . 000000000000010000000000BBBBB . . . .    The rest is omitted.-   C) The fore is omitted . . . 101001010111011010101011CCCCC . . . .    The rest is omitted.

A) indicates a packet received from the turbo processor 250, B)indicates an RS re-encoded packet, and C) indicates a packet obtained byperforming exclusive OR on the received packet and the RS re-encodedpacket using the adder 430. When an underlined part of the receivedpacket of A) is input to the trellis encoder block 410, the trellisencoder block 410 is initialized. In this case, a value corresponding toa value pre-stored in the trellis encoder block 410 is provided to theRS re-encoder 420, and the RS re-encoder 420 adds parity to the providedvalue to output the RS re-encoded packet of B). An underline part of theRS re-encoded packet of B) represents a changed value corresponding tothe underlined part of the received packet of A). Parity correspondingto the underline part of the RS re-encoded packet of B) is regeneratedas “BBBBB.”

The adder 430 performs the exclusive OR on the received packet of A) andthe RS re-encoded packet of B) to output the packet of C). Consideringthe packet of C), the underlined part of the received packet of A) ischanged into “01” in the packet of C), and parity of the received packetof A) is changed from “AAAAA” into “CCCCC” in the packet of C).

When initialization and parity correction are completed, the multiplexer440 operates in a general operation mode to provide the dualtransmission stream to the trellis encoder block 410.

The mapper 450 maps the trellis encoded packet into 8-level symbols andoutputs the 8-level symbols. In detail, the mapper 450 may map thetrellis encoded packet as shown in Table 1 below.

TABLE 1 Z2 Z1 Z0 R 0 0 0 −7 0 0 1 −5 0 1 0 −3 0 1 1 −1 1 0 0 +1 1 0 1 +31 1 0 +5 1 1 1 +7

As shown in Table 1 above, Z0, Z1, and Z2 are trellis encoding valuesoutput from the trellis encoder block 410, and R represents mappingoutput values corresponding to the trellis encoding values. In otherwords, if the trellis encoding values are output as “0, 0, 0,” themapper 450 outputs “−7” as a mapping output value.

FIG. 13 is a block diagram illustrating a configuration of the trellisencoder block 410 according to an embodiment of the present invention.Referring to FIG. 13, the trellis encoder block 410 includes a splitter411, a plurality of trellis encoders 412-1 through 412-12, and anencoding output unit 413.

The splitter 411 sequentially outputs streams output from themultiplexer 440 to the plurality of trellis encoders 412-1 through412-12. In this case, the streams may be output in the unit of byte.

The plurality of trellis encoders 412-1 through 412-12 trellis encodeand output the streams. In this case, the trellis encoders 412-1 through412-12 are sequentially selected to sequentially output trellis encodingvalues of the trellis encoders 412-1 through 412-12. During an initialsection, the trellis encoders 412-1 through 412-12 provide valuespre-stored in memories (not shown) of the trellis encoders 412-1 through412-12 as initial values to the RS re-encoder 420. The RS re-encoder 420adds parity to the provided initial values and outputs the additionresult to the adder 430 to correct the parity.

The encoding output unit 413 sequentially detects the trellis encodingvalues output from the trellis encoders 412-1 through 412-12 and outputsthe trellis encoding values to the mapper 450.

The trellis encoders 412-1 through 412-12 each includes a plurality ofmemories (not shown) and perform trellis encoding using the memories. Inthis case, initialization is performed immediately before an area, withan SRS, is trellis encoded. The memories are reset by theinitialization. In this process, values pre-stored in the memories areprovided as initial values to the RS re-encoder 420.

In detail, each of the trellis encoders 412-1 through 412-12 may includethree memories, i.e., first through third memories (not shown). When theinitialization is performed, the first memory outputs a pre-stored valueas an initial value (referred to as a first initial value). Also, thethird memory is initialized and simultaneously shifts a pre-stored valueto the second memory. A value pre-stored in the second memory is outputas an initial value (referred to as a second initial value) according tothe shifting operation. The RS re-encoder 420 combines the first andsecond values and uses the combined value as an initial value.

The second and third memories are arranged in a line to perform shiftingoperations. Thus, a control signal having 2 symbols is required toinitialize the second and third memories. Also, 8 initial value states“000,” “111,” “001,” “010,” “100,” “110,” “101,” “011” may be formedusing the three memories. Values “X0” and “X1” indicating the first andsecond initial values may be provided to the RS re-encoder 420 to changeparity.

Referring to FIG. 8, the sync signal multiplexer 270 adds a segment syncsignal and a field sync signal to the trellis encoded dual transmissionstream and multiplexes the dual transmission stream.

The pilot inserter 280 adds a predetermined DC value to the dualtransmission stream to which the segment sync signal and the field syncsignal have been added to insert a pilot into the dual transmissionstream.

The pre-equalizer 285 equalizes the dual transmission stream into whichthe pilot has been inserted so as to minimize an inter-symbolinterference (ISI).

The VSB modulator 290 VSB modulates the equalized dual transmissionstream.

The RF modulator 295 modulates the VSB modulated dual transmissionstream into a signal in an RF channel band and outputs the signal.

FIG. 14 is a block diagram illustrating a configuration of the receiver300 of the digital broadcasting system shown in FIG. 3, according to anembodiment of the present invention. Referring to FIG. 14, the receiver300 includes a demodulator 310, an equalizer 320, a Viterbi decoder 330,a turbo decoder 340, a turbo inserter 350, a deinterleaver 360, an RSdecoder 370, a derandomizer 380, and a turbo demultiplexer 390.

The demodulator 310 detects synchronization from the dual transmissionstream according to the sync signal added to the baseband signal of thedual transmission stream and demodulates the dual transmission stream.

The equalizer 320 equalizes the demodulated dual transmission stream tocompensate for a distortion of a channel caused by a multi-path of thechannel. The dual transmission stream equalized by the equalizer 320 isprovided to the viterbi decoder 330 and the turbo decoder 340.

The Viterbi decoder 330 performs error correction of the equalized dualtransmission stream decodes the error-corrected equalized dualtransmission stream into error-correcting encoded symbols.

The turbo decoder 340 detects only the turbo stream of the equalizeddual transmission stream and turbo decodes the turbo stream. Turbodecoding represents a process of decoding the turbo stream. This will bedescribed in detail later.

The turbo inserter 350 inserts the turbo stream turbo decoded by theturbo decoder 340 into the Viterbi decoded dual transmission stream. Inthis case, the turbo inserter 350 may detect the turbo stream from theturbo decoded dual transmission stream and insert the turbo stream intoan area corresponding to the turbo stream of the Viterbi decoded dualtransmission stream. The area corresponding to the turbo stream may be aportion of a packet adaptation field or the whole packet adaptationfield. The packet adaptation field represents an area which is formed ineach packet of a dual transmission stream and in which an SRS, turbostream data, and the like are to be recorded.

The deinterleaver 360 deinterleaves the dual transmission stream intowhich the turbo stream has been inserted.

The RS decoder 370 decodes deinterleaved packets to correct an error.

The derandomizer 380 derandomizes the error corrected packets, and theturbo demultiplexer 390 demultiplexes the derandomized packets torestore the normal stream and the turbo stream.

FIG. 15 is a block diagram illustrating a configuration of the turbodecoder 340 according to an embodiment of the present invention.Referring to FIG. 15, the turbo decoder 340 includes a trellis decoder341, an outer deinterleaver 342, an outer map decoder 343, an outerinterleaver 344, a frame formatter 345, and a symbol deinterleaver 346.

The trellis decoder 341 trellis decodes the turbo stream of theequalized dual transmission stream and provides the trellis decodedturbo stream to the outer deinterleaver 342.

The outer deinterleaver 342 deinterleaves the trellis decoded turbostream.

The outer map decoder 343 may convolution decode the deinterleaved turbostream. The outer map decoder 343 outputs soft decision and harddecision output values depending on the result of convolution decoding.Here, the soft and hard decision output values depend on a matrix of theturbo stream. For example, if the matrix of the turbo stream is “0.8,”the soft decision output value is output as “0.8.” If the matrix of theturbo stream is “1,” the hard decision output value is output.

The hard decision output value of the outer map decoder 343 is providedto the frame formatter 345. In this case, the hard decision output valuerepresents the turbo stream.

The frame formatter 345 formats the convolution decoded hard decisionturbo stream to a frame of the dual transmission stream.

The symbol deinterleaver 346 may deinterleave the frame formatted turbostream from a symbol unit to a byte unit. The deinterleaving from thesymbol unit to the byte unit may be easily understood with reference toTable D5.2 of “US ATSC DTV Standards (A/53)”, and thus its detaileddescription will be omitted. The symbol deinterleaver 346 is shown inFIG. 15 but may be omitted.

If the outer map decoder 343 outputs the soft decision output value, theouter interleaver 344 interleaves the turbo stream and provides theinterleaved turbo stream to the trellis decoder 341. The trellis decoder341 trellis decodes the interleaved turbo stream and provides thetrellis decoded turbo stream to the outer deinterleaver 342. The outerdeinterleaver 342 deinterleaves the trellis decoded turbo stream andprovides the deinterleaved turbo stream to the outer map decoder 343.The operations of the trellis decoder 341, the outer deinterleaver 342,and the outer interleaver 344 may be repeatedly performed until the harddecision output value is output. Thus, a reliable decoded value can beobtained.

FIG. 16 is a block diagram illustrating a configuration of the turbodemultiplexer 390 of the receiver 300 shown in FIG. 14. Referring toFIG. 16, the turbo demultiplexer 390 includes a transmission stream (TS)demultiplexer 391, a condenser 393, an RS decoder 394, and first andsecond sync signal inserters 392 and 395.

The TS demultipexer 391 demultipexes the derandomized packets into thenormal stream and the turbo stream.

A sync signal is inserted into the normal stream demultiplexed by the TSdemultiplexer 391 using the first sync signal inserter 392 to restorethe normal stream of 188 bytes.

The condenser 393 removes a placeholder from the deinterleaved turbostream. The placeholder may be a parity insertion area for RS encoding aturbo stream in a digital broadcasting transmitting system. If theplaceholder is formed at a rate of ¼ or ½, a magnitude of the turbostream may be reduced by the rate of ¼ or ½.

The RS decoder 394 decodes the turbo stream from which the placeholderhas been removed.

The second sync signal inserter 395 inserts a sync signal into thedecoded turbo stream to restore the turbo stream of 188 bytes. If thesync signal of the turbo stream is removed during the generation of thedual transmission stream, a process of inserting a sync signal using thesecond sync signal inserter 395 to regenerate the turbo stream isrequired.

FIG. 17 is a block diagram illustrating a configuration of the turbodemultiplexer 390 according to another embodiment of the presentinvention. Referring to FIG. 17, the turbo demultipexer 390 includes aTS demultiplexer 391, a sync signal inserter 397, a condenser 393, an RSdecoder 394, and a sync signal detector 396. Different from thedescription with reference to FIG. 17, a sync signal of the turbo streammay not be removed during the generation of the dual transmissionstream. In this case, the sync signal of the turbo stream is alsoreceived, and thus a sync signal does not need to be inserted into thedecoded turbo stream. However, similar to the description with referenceto FIG. 17, the sync signal inserter 397 inserts a sync signal into thenormal stream demultiplexed by the TS demultiplexer 391 to restore thenormal stream of 188 bytes.

The sync signal detector 396 receives the turbo stream from which theplaceholder has been removed, checks a value “0x47” of the sync signalof the received turbo stream, and outputs the turbo stream from a byteafter the sync signal up to 187 bytes to the RS decoder 394. Here, thevalue “0x47” of the sync signal indicates a value of a sync signalexisting in each packet, and one packet includes 187 bytes except onebyte of the sync signal. The sync signal detector 396 may detect theturbo stream from the value of the sync signal up to 187 bytes.

The RS decoder 394 corrects an error of the turbo stream of 188 bytesfrom which the sync signal has been detected and restores the turbostream.

The turbo demultiplexer 390 shown in FIG. 16 or 17 may further include adeinterleaver (not shown). In other words, if the transmission streamgenerator 100 further includes an interleaver, the turbo demultiplexer390 of the receiver 300 may further include the deinterleaver.

A digital broadcasting method according to an embodiment of the presentinvention includes: generating a dual transmission stream including aturbo stream and a normal stream; turbo decoding and transmitting onlythe turbo stream of the dual transmission stream; and receiving the dualtransmission stream to separately decode the normal stream and the turbostream so as to restore normal stream data and turbo stream data.

FIG. 18 is a flowchart illustrating a method of generating andtransmitting a dual transmission stream according to an embodiment ofthe present invention. Referring to FIG. 18, in operation S610, a dualtransmission stream is generated. In detail, parity insertion areas areformed in a turbo stream, an adaptation field is formed in a normalstream, and the turbo stream and the normal stream are multiplexed togenerate the dual transmission stream.

In operation S620, the dual transmission stream is randomized. Inoperation S630, an SRS is inserted into a portion of the adaptationfield.

In operation S640, the dual transmission stream into which the SRS hasbeen inserted is encoded. In operation S650, the encoded dualtransmission stream is interleaved.

In operation S660, turbo processing is performed. The turbo processingis a process where only the turbo stream is detected from the dualtransmission stream, encoded, interleaved, and inserted into the dualtransmission stream. In this case, operation S660 is performed afteroperation S640. Thus, a parity compensation operation is additionallyperformed to prevent parity from varying with the turbo processing.

In operation S670, trellis encoding and/or parity correction areperformed. Thereafter, a sync signal is multiplexed, a pilot is insertedinto the dual transmission stream, and the dual transmission stream isequalized, modulated, and transmitted. The detailed description of thishas been described above and thus will be omitted.

FIG. 19 is a flowchart illustrating a method of receiving a dualtransmission stream according to an embodiment of the present invention.Referring to FIG. 19, in operation S710, a dual transmission stream isreceived and demodulated. In operation S720, the demodulated dualtransmission stream is equalized. A normal stream and a turbo stream aresplit from the equalized dual transmission stream. In operation S730,the normal stream and the turbo stream are separately decoded. Thedecoding of the turbo stream may be performed using a turbo decoderhaving a structure as shown in FIG. 15. If the normal stream and theturbo stream are completely decoded, the turbo stream is re-insertedinto the dual transmission stream to reconstitute the dual transmissionstream in operation S740.

In operation S750, the reconstituted dual transmission stream isdeinterleaved. In operation S760, the deinterleaved dual transmissionstream is RS decoded. In operation S770, the RS decoded dualtransmission stream is derandomized. In operation S780, the dualtransmission stream is demultiplexed to restore turbo stream data andnormal stream data.

FIG. 20 is a flowchart illustrating a turbo decoding method according toan embodiment of the present invention. Referring to FIG. 20, inoperation S810, a turbo stream of a dual transmission stream is trellisdecoded. In operation S820, the trellis decoded turbo stream is outerdeinterleaved. In operation S830, the outer deinterleaved turbo streamis outer decoded.

If a hard decision output value is output through outer decoding, thehard decision turbo stream is formatted to a frame of the dualtransmission stream in operation S850. In operation S860, the turbostream is symbol interleaved.

If a soft decision output value is output through the outer decoding,operation S840 is performed to outer interleave the trellis decodedturbo stream. Operations S810 and 820 are performed again to trellisdecode and outer deinterleave the outer interleaved turbo stream. Thus,a reliable hard decision turbo stream can be obtained.

FIG. 21 is a view illustrating a structure of a dual transmission streamprocessed by a digital broadcasting system of an embodiment of thepresent invention. Referring to FIG. 21, in one field of the dualtransmission stream, 78 turbo stream packets are inserted into 312segment packets. In the dual transmission stream, a packet (188 bytes)of turbo streams and three packets (188 bytes) of normal streams arerepeated in a ratio of 1:3. If 70 packets of turbo streams are insertedinto 312 segments of the dual transmission stream, a packet of turbostreams and three packets of normal streams are repeated 70 times in aratio of 1:3, and the remaining 32 packets are constituted as normalstream packets in the dual transmission stream. An SRS having an S bytesize is inserted into each packet, and thus a size of the turbo streamis 182-S bytes.

A broadcasting signal corresponding to a turbo stream and a normalstream can be viewed using the above-described broadcasting system andmethod.

As described above, according to an embodiment of the present invention,a broadcasting service can be performed using a dual transmission streamincluding a turbo stream and a normal stream. Thus, specific data can berobustly processed and transmitted. As a result, the broadcastingservice can be efficiently offered. Also, an SRS can be inserted intothe dual transmission stream so that a receiver can easily check a stateof a channel. Thus, a compensation degree can be determined. Inparticular, the above-described operations can be performed using atransmitter and the receiver having simple structures. As a result,reception sensitivity of an ATSC VSB way such as in a United Statesterrestrial DTV system can be efficiently improved.

Although a few embodiments of the present invention have been shown anddescribed, it would be appreciated by those skilled in the art thatchanges may be made in this embodiment without departing from theprinciples and spirit of the invention, the scope of which is defined inthe claims and their equivalents.

What is claimed is:
 1. A digital broadcasting transmitter processing astream to be robust against errors, the digital broadcasting transmittercomprising: a first converter receiving a stream of a byte unit andconverting the received stream; an encoder encoding the stream convertedby the first converter and outputting a stream of a symbol unit; aninterleaver interleaving the stream output from the encoder; and asecond converter converting the interleaved stream from a symbol unitinto a byte unit, wherein the digital broadcasting transmitter furthercomprises a trellis encoder which trellis-encodes the stream convertedby the second converter, and wherein the trellis encoder initializes aninternal memory before known data, which is previously known between thedigital broadcasting transmitter and a digital broadcasting receiver, istrellis encoded.
 2. The stream processing device as claimed in claim 1,further comprising: a stuffer multiplexing the stream and a normalstream to constitute a transmission stream.
 3. The digital broadcastingtransmitter as claimed in claim 1, further comprising a signal inserterwhich inserts data for initialization and the known data to the robuststream.
 4. The digital broadcasting transmitter as claimed in claim 3,wherein the data for the initialization is two symbols used forinitialization of the trellis encoder.
 5. A stream processing method toprocess a stream to be transmitted by a digital broadcasting transmitterso that the stream is robust against errors, the stream processingmethod comprising: a first converting operation for receiving a streamof a byte unit and converting the received stream; an outer-encodingoperation for encoding the converted stream and outputting a stream of asymbol unit; an outer-interleaving operation for interleaving theencoded stream; and a second converting operation for converting theinterleaved stream from a symbol unit into a byte unit, wherein thedigital broadcasting transmitter further comprises a trellis encoderwhich trellis-encodes the stream converted at the second convertingoperation, and wherein the trellis encoder initializes an internalmemory before known data, which is previously known between the digitalbroadcasting transmitter and a digital broadcasting receiver, is trellisencoded.
 6. The stream processing method as claimed in claim 5, furthercomprising: multiplexing the stream and a normal stream to constitute atransmission stream.
 7. The stream processing method as claimed in claim5, further comprising: inserting data for initialization and the knowndata to the robust stream.
 8. The stream processing method as claimed inclaim 7, wherein the data for initialization is two symbols used for theinitialization of the trellis encoder.